Reland `coverableLineCache` optimisation (#136851) (#137385)

Relands #136851, which was rolled back in #137121

package:coverage has been rolled, so the breakages should be fixed.
Also, in this reland I've changed the `coverableLineCache` parameter to
be optional, which is safer.

packages/flutter_tools/lib/src/test/coverage_collector.dart

@@ -37,6 +37,7 @@ class CoverageCollector extends TestWatcher {
 
   final coverage.Resolver? resolver;
   final Map<String, List<List<int>>?> _ignoredLinesInFilesCache = <String, List<List<int>>?>{};
+  final Map<String, Set<int>> _coverableLineCache = <String, Set<int>>{};
 
   final TestTimeRecorder? testTimeRecorder;
 
@@ -103,7 +104,11 @@ class CoverageCollector extends TestWatcher {
   Future<void> collectCoverageIsolate(Uri vmServiceUri) async {
     _logMessage('collecting coverage data from $vmServiceUri...');
     final Map<String, dynamic> data = await collect(
-        vmServiceUri, libraryNames, branchCoverage: branchCoverage);
+      vmServiceUri,
+      libraryNames,
+      branchCoverage: branchCoverage,
+      coverableLineCache: _coverableLineCache,
+    );
 
     _logMessage('($vmServiceUri): collected coverage data; merging...');
     _addHitmap(await coverage.HitMap.parseJson(
@@ -145,9 +150,12 @@ class CoverageCollector extends TestWatcher {
       .then((Uri? vmServiceUri) {
         _logMessage('collecting coverage data from $testDevice at $vmServiceUri...');
         return collect(
-            vmServiceUri!, libraryNames, serviceOverride: serviceOverride,
-            branchCoverage: branchCoverage)
-          .then<void>((Map<String, dynamic> result) {
+          vmServiceUri!,
+          libraryNames,
+          serviceOverride: serviceOverride,
+          branchCoverage: branchCoverage,
+          coverableLineCache: _coverableLineCache,
+        ).then<void>((Map<String, dynamic> result) {
             _logMessage('Collected coverage data.');
             data = result;
           });
@@ -267,9 +275,12 @@ Future<Map<String, dynamic>> collect(Uri serviceUri, Set<String>? libraryNames,
   @visibleForTesting bool forceSequential = false,
   @visibleForTesting FlutterVmService? serviceOverride,
   bool branchCoverage = false,
+  Map<String, Set<int>>? coverableLineCache,
 }) {
   return coverage.collect(
-      serviceUri, false, false, false, libraryNames,
-      serviceOverrideForTesting: serviceOverride?.service,
-      branchCoverage: branchCoverage);
+    serviceUri, false, false, false, libraryNames,
+    serviceOverrideForTesting: serviceOverride?.service,
+    branchCoverage: branchCoverage,
+    coverableLineCache: coverableLineCache,
+  );
 }

packages/flutter_tools/test/general.shard/coverage_collector_test.dart

@@ -53,6 +53,7 @@ void main() {
       Uri(),
       <String>{'foo'},
       serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{'type': 'CodeCoverage', 'coverage': <Object>[]});
@@ -123,6 +124,7 @@ void main() {
       Uri(),
       <String>{'foo'},
       serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{
@@ -151,6 +153,7 @@ void main() {
       Uri(),
       null,
       serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{
@@ -237,6 +240,7 @@ void main() {
       Uri(),
       <String>{'foo'},
       serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{
@@ -311,6 +315,7 @@ void main() {
       Uri(),
       null,
       serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{
@@ -401,6 +406,7 @@ void main() {
       <String>{'foo'},
       serviceOverride: fakeVmServiceHost.vmService,
       branchCoverage: true,
+      coverableLineCache: <String, Set<int>>{},
     );
 
     expect(result, <String, Object>{
@@ -601,6 +607,179 @@ void main() {
       tempDir?.deleteSync(recursive: true);
     }
   });
+
+  testWithoutContext('Coverage collector fills coverableLineCache', () async {
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(
+      requests: <VmServiceExpectation>[
+        FakeVmServiceRequest(
+          method: 'getVM',
+          jsonResponse: (VM.parse(<String, Object>{})!
+            ..isolates = <IsolateRef>[
+              IsolateRef.parse(<String, Object>{
+                'id': '1',
+              })!,
+            ]
+          ).toJson(),
+        ),
+        FakeVmServiceRequest(
+          method: 'getVersion',
+          jsonResponse: Version(major: 4, minor: 13).toJson(),
+        ),
+        FakeVmServiceRequest(
+          method: 'getSourceReport',
+          args: <String, Object>{
+            'isolateId': '1',
+            'reports': <Object>['Coverage'],
+            'forceCompile': true,
+            'reportLines': true,
+            'libraryFilters': <String>['package:foo/'],
+            'librariesAlreadyCompiled': <String>[],
+          },
+          jsonResponse: SourceReport(
+            ranges: <SourceReportRange>[
+              SourceReportRange(
+                scriptIndex: 0,
+                startPos: 0,
+                endPos: 0,
+                compiled: true,
+                coverage: SourceReportCoverage(
+                  hits: <int>[1, 3],
+                  misses: <int>[2],
+                ),
+              ),
+            ],
+            scripts: <ScriptRef>[
+              ScriptRef(
+                uri: 'package:foo/foo.dart',
+                id: '1',
+              ),
+            ],
+          ).toJson(),
+        ),
+      ],
+    );
+
+    final Map<String, Set<int>> coverableLineCache = <String, Set<int>>{};
+    final Map<String, Object?> result = await collect(
+      Uri(),
+      <String>{'foo'},
+      serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: coverableLineCache,
+    );
+
+    expect(result, <String, Object>{
+      'type': 'CodeCoverage',
+      'coverage': <Object>[
+        <String, Object>{
+          'source': 'package:foo/foo.dart',
+          'script': <String, Object>{
+            'type': '@Script',
+            'fixedId': true,
+            'id': 'libraries/1/scripts/package%3Afoo%2Ffoo.dart',
+            'uri': 'package:foo/foo.dart',
+            '_kind': 'library',
+          },
+          'hits': <Object>[1, 1, 3, 1, 2, 0],
+        },
+      ],
+    });
+
+    // coverableLineCache should contain every line mentioned in the report.
+    expect(coverableLineCache, <String, Set<int>>{
+      'package:foo/foo.dart': <int>{1, 2, 3},
+    });
+
+    expect(fakeVmServiceHost.hasRemainingExpectations, false);
+  });
+
+  testWithoutContext('Coverage collector avoids recompiling libraries in coverableLineCache', () async {
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(
+      requests: <VmServiceExpectation>[
+        FakeVmServiceRequest(
+          method: 'getVM',
+          jsonResponse: (VM.parse(<String, Object>{})!
+            ..isolates = <IsolateRef>[
+              IsolateRef.parse(<String, Object>{
+                'id': '1',
+              })!,
+            ]
+          ).toJson(),
+        ),
+        FakeVmServiceRequest(
+          method: 'getVersion',
+          jsonResponse: Version(major: 4, minor: 13).toJson(),
+        ),
+
+        // This collection sets librariesAlreadyCompiled. The response doesn't
+        // include any misses.
+        FakeVmServiceRequest(
+          method: 'getSourceReport',
+          args: <String, Object>{
+            'isolateId': '1',
+            'reports': <Object>['Coverage'],
+            'forceCompile': true,
+            'reportLines': true,
+            'libraryFilters': <String>['package:foo/'],
+            'librariesAlreadyCompiled': <String>['package:foo/foo.dart'],
+          },
+          jsonResponse: SourceReport(
+            ranges: <SourceReportRange>[
+              SourceReportRange(
+                scriptIndex: 0,
+                startPos: 0,
+                endPos: 0,
+                compiled: true,
+                coverage: SourceReportCoverage(
+                  hits: <int>[1, 3],
+                  misses: <int>[],
+                ),
+              ),
+            ],
+            scripts: <ScriptRef>[
+              ScriptRef(
+                uri: 'package:foo/foo.dart',
+                id: '1',
+              ),
+            ],
+          ).toJson(),
+        ),
+      ],
+    );
+
+    final Map<String, Set<int>> coverableLineCache = <String, Set<int>>{
+      'package:foo/foo.dart': <int>{1, 2, 3},
+    };
+    final Map<String, Object?> result2 = await collect(
+      Uri(),
+      <String>{'foo'},
+      serviceOverride: fakeVmServiceHost.vmService,
+      coverableLineCache: coverableLineCache,
+    );
+
+    // Expect that line 2 is marked as missed, even though it wasn't mentioned
+    // in the getSourceReport response.
+    expect(result2, <String, Object>{
+      'type': 'CodeCoverage',
+      'coverage': <Object>[
+        <String, Object>{
+          'source': 'package:foo/foo.dart',
+          'script': <String, Object>{
+            'type': '@Script',
+            'fixedId': true,
+            'id': 'libraries/1/scripts/package%3Afoo%2Ffoo.dart',
+            'uri': 'package:foo/foo.dart',
+            '_kind': 'library',
+          },
+          'hits': <Object>[1, 1, 2, 0, 3, 1],
+        },
+      ],
+    });
+    expect(coverableLineCache, <String, Set<int>>{
+      'package:foo/foo.dart': <int>{1, 2, 3},
+    });
+
+    expect(fakeVmServiceHost.hasRemainingExpectations, false);
+  });
 }
 
 File writeFooBarPackagesJson(Directory tempDir) {